For the past little while, I've been working really hard to collect all of the dragon priest masks, and I'm missing only one. The problem is that, the mask that I'm missing is Nahkriin. A friend told me that you can only get Nahkriin (Trying not to spoil anything) on the mission right where Odahviing drops you off near the portal to Sovngarde. I was a really low level when I beat the main quest, so almost unable to fight the dragon priest, (and not knowing what it was) I sprinted right by it and for the portal. I've put too many hours into this account to start all over, and It doesn't seem fair that I can't get the mask.
Should Bethesda get out of their way to allow players to grab the mask later on? Has this happened to anyone else?